While I don't feel that there is only one right way to teach literature and writing, I am less open to instructional methods for grammar, mechanics, and style. Based on what I have seen over the years in student writing as a result of progressive grammar methods, I am now more convinced than ever that grammar is best taught the old-fashioned way, which is systematic and incremental. As the "math" of language, systematic, yearly instruction is the best way to master the complexity of the English language. To teach students grammar for mastery and improved writing, I recommend a four-pronged approach: 1. Systematic, leveled instruction every year of grade school (though not necessarily every day or every semester) 2. Regular, sentence-level grammar analysis 3. Regular editing and proofreading practice on controlled writing models (finding mistakes in the writing of others) 4. Regular writing assignments that culminates in polished, final drafts (finding mistakes in one's own writing)
Several respected grammar programs are on the market for homeschoolers, but I have listed my preferences below:
For systematic instruction (prong 1): Warriner's English Grammar and Composition series (6th-12th grades): This classic school textbook series is widely considered to be the best one ever published because of its thoroughness and clarity. It is also cleverly designed to double as a compact reference manual. The original series is now out of print, but many used vendors sell them. Teacher's guides can be difficult to find, but Mother of Divine Grace School still uses this program and sells answer keys. You may also find the Warriner's revised edition available with answer keys. The revised series is called Warriner's Handbook and may be available with teacher's guides from Holt or through used vendors. CAUTION: The Warriner's series was published in several editions, which are most easily identifiable by their cover photo and year of publication. Because answer keys and teacher manuals are harder to find than textbooks, I suggest you find one of those first and then pair it with the right textbook.
* Memoria Press English Grammar Recitation series: This is the other systematic grammar program I recommend and have used personally. It is similar to Warriner's in its approach, but it is designed for students in grades 1-8. Because of its plain format, though, high school students may use it with dignity.
For sentence-level grammar analysis (prong 2): Although I advocate traditional grammar instruction, I disagree with the common idea that frequent diagramming is important to a good grammar study. I do require some diagramming, since it is valuable for helping students understand how sentence parts are related to each other, but I feel that the four-level analysis method developed by Michael Clay Thompson is more valuable in the long run for giving students a thorough understanding of English grammar. I have adapted his method to my own online classes and use it regularly to facilitate mastery. Thompson also offers systematic instruction that may be a strong alternative to Warriner's --though having not used it, I can't say for sure.
For editing and proofreading practice (prong 3): This goes by several names. Probably the oldest term for it is Daily Oral Language, where students correct a writing model that has a set number of grammatical and mechanical mistakes in it. Several homeschool and classroom resources offer this kind of practice, and they are probably all worthwhile. However, I am most familiar with the Fix-it!: Grammar program from the Institute for Excellence in Writing. It is appealing to students because of its use of interesting stories.
If the above suggestions don't fit your needs, consider the following programs:
Analytical Grammar series (Analytical Grammar)
Easy Grammar and supplemental programs, by Wanda C. Phillips (Easy Grammar Systems)
Grammar for the Well-Trained Mind, by Susan Wise Bauer (Well-Trained Mind Press)
Jensen's Grammar, by Frode Jensen (Master Books)
Write Source Skills Book series -- classroom resource; not systematic, full program, just useful practice and review (Houghton Mifflin Harcourt)
The Blue Book of Grammar and Punctuation, by Jane Straus -- published for adult learners with useful website: grammarbook.com